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Thread: Has anyone ever tried to implement a digital poti?

  1. #1
    Flashaholic doc_felixander's Avatar
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    Default Has anyone ever tried to implement a digital poti?

    Aye!! My first post!!!!

    I've just ordered a cheapo Golston 7W CR123, and though I'm expecting it to be definitely worth it's money, I'm already considering improving a few things.

    First of all, I'll get rid of that resistor, which eats up a few watts.
    As I want it to run on an 18650 LiIo, I'll need a converter to preserve as much as possible of its original brightness.

    I think the MAXIM 1797 (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2377) should do, it doesn't need current regulation anyway. gives me max 5 (5.5?) V max, 3.3V min, at up to 1.25 (1.0 typ.) A.

    Here is the tricky part: ALthough i bought this thing because it is damn bright and really cheap, it would be nice to dim it for longer runtime, which should work due to the high efficiency of those converters.
    Designing a circuit that gives me HDS- or Gladius-like features should be impossible due to my limited skills, BUT as mentioned above, that max 1797 can be regulated from 3.3 to 5V using a simple voltage divider.

    As you can imagine, I don't want to build a mechanical poti into that flashlight (looks like crap, first thing to break off, not waterproof anymore etc......), and the next thing that came into my mind was a digital poti, you know, simply 2 buttons to increase/ decrease brightness.

    Doing some research, I stumbled across the MAX547x series (http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4092).
    A fully integrated circuit which features 32 steps, comes in a really tiny package (8SOT23) and remembers the last setting. (and is cheap).
    Should be small enough to fit on the driver PCB and draws only 1µA in idle state.

    Finally, I_ll have to add 2 buttons to the tube, preferrably with waterproof rubber cover......

    Has anyone ever built such a thing? Any ideas?

  2. #2
    Flashaholic* Kryosphinx's Avatar
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    Default Re: Has anyone ever tried to implement a digital poti?

    Check out the D2DIM at taskled.com
    Got busted lights? Send me a PM and depending on the situation, I'll take 'em off your hands. I always like a good modding challenge.

  3. #3
    Flashaholic doc_felixander's Avatar
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    Default Re: Has anyone ever tried to implement a digital poti?

    aaaah......just stumbled over the FLUPIC.....that's it!

  4. #4
    *Flashaholic* andrewwynn's Avatar
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    Default Re: Has anyone ever tried to implement a digital poti?

    http://vip8.rouse.com

    i put an 8-level digital pot in place of my 3-level switch in my VIP.. subsequently i upgraded to using a UX1N emitter so i can use R123, but since the Vbat is so much higher.. i still don't get full range of brightness.. only the top 5 levels work now.. it's sweet though. I think if i put in an K2.. the higher Vf will cure that and i'll get 8 levels again.

    The D2DIM is pure gold from the standpoint of saving battery if you aren't worried about level output... one button control.. pre-built construction!

    -awr


    Regulated hotwire 'the hotdriver' also for Surefire M6 • 3-level high-power LED drop-in for mag. the 'BAM!' click here
    I have disabled PMs.. use the 'email' link instead!Genesis 1:3 And God said, "Let there be light," and there was light...

  5. #5
    Flashaholic*
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    Default Re: Has anyone ever tried to implement a digital poti?

    The FluPIC is exactly what you were looking for...

    Keep in mind, output is not regulated...

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